It has always been a challenge for manufacturers of large composite parts, particularly wind turbine blades, to obtain accurate alignment between their separate upper and lower moulds, and to adjust the required values of geometry parameters ‘overbite’ and ‘gap’.
Generally two types of alignment device have been applied to correct or adjust overbite and gap:                1. The alignment pin or dowel, consisting of a round or conical bar fixed to one mould, oriented more or less normal to the mould mating face, entering in a hole on the opposite mould. The alignment pin does not provide a means for adjusting gap, only overbite.        2. The alignment key or block, featuring a trapezoidal piece fixed to one mould, oriented more of less normal to the mould mating face, entering a V block or groove on the opposite mould.        
The alignment pin or dowel has been traditionally totally fixed to one mould, placed as accurately as possible, and not adjustable in any way.
The alignment key or block has been traditionally adjustable by means of slotted holes and bolts. In some cases, the open space distance between the moulds, or gap, has been adjusted by shims. Generally adjustment has been laborious, requiring first opening of the mould, then loosening of the locking bolts, perhaps removal or addition of shims, fine adjustment of the alignment key position by hand or perhaps by tapping with a hammer, tightening the locking bolts, and rechecking the mould alignment and gap. A major disadvantage is that the gap cannot be adjusted without accidentally perturbing the overbite setting. Anyway, performing such adjustments on a large mould normally has required considerable experience and skill, and cannot be accomplished quickly.